Second baseman Marco Scutaro hit the game-winning single with two outs in the top of the 10th inning to score Ryan Theriot, and the Giants completed a four-game sweep of the Detroit Tigers with a 4-3 victory Sunday night to win the World Series.

Giants closer Sergio Romo struck out the side in the bottom of the 10th inning, fanning Tigers third baseman Miguel Cabrera looking for the final out. Romo, known for his dominant slider against right-handed hitters, threw his only fastball to Cabrera to end it.

"Tonight was a fitting way for us to end it," Giants catcher Buster Posey said. "Those guys played hard, they didn't stop. It's an unbelievable feeling."

The final pitch was a stunner after Romo threw Cabrera five consecutive sliders, leaving the count at 2-2.

"I know he's the best hitter in baseball, but I wasn't going to let him beat me," Romo said. "I was going to get him out. I was going to find a way. I had my whole team relying on me there, and I used that energy on the final pitch when I went to the fastball."

The 89 mph pitch went right down the middle.

"I feel embarrassed I struck out and made the last out of the World Series," Cabrera said. "It's the worst feeling in the world."

Theriot started the winning rally with a single off losing pitcher Phil Coke and was bunted to second by Brandon Crawford.

Coke struck out Angel Pagan, but Scutaro followed by dropping a single into right-center field to score Theriot.

"You kind of get worried when guys like Marco come up," Giants starting pitcher Matt Cain. "You worry that maybe they've used all their clutch hits up and if the baseball gods might turn against you. He had one more left in him, and it was the biggest one you needed."

Santiago Casilla got the last out in the ninth inning to get credit for the win as the National League West champion Giants became the 24th team to sweep a World Series.

The Tigers managed just six runs in the series and were shut out in Games 2 and 3.

"I'm a little bit flabbergasted, to be honest with you," Tigers manager Jim Leyland said about being swept. "It's a freaky game and it happened. So be it."

Giants manager Bruce Bochy was just surprised about the sweep and winning two World Series in three years.

"It's really just amazing," Bochy said. "I know how hard it is just to get to this point. To be able to a sweep a World Series and win two of them in three years, it's just unbelievable. Our guys fought all year, and they deserve this. They played like champions."

The likely Most Valuable Players in their respective leagues -- Cabrera and Posey -- both homered as the teams went into extra innings tied at 3-3.

Cabrera belted a two-run home run off Matt Cain in the third inning to put the Tigers ahead 2-1 as Detroit finally took a lead for the first time in the series. It was just the second home run in 54 postseason plate appearances for Cabrera after he won the American League Triple Crown by leading the league with a .330 batting average, 44 home runs and 139 RBI.

Cabrera hit what looked like a routine popup to right field off the bat. However, the ball kept carrying on a gusty night until it landed in the first row of seats.

With the Tigers trailing 1-0 in the third, Austin Jackson drew a one-out walk and moved to second when Quintin Berry grounded out while unsuccessfully trying to bunt for a base hit. Cabrera followed with his home run.

Cabrera's hit was just the Tigers' second in 12 at-bats with runners in scoring position in the series.

Posey put the Giants back ahead 3-2 when he hit a two-run shot in the sixth inning off Tigers starter Max Scherzer. Posey, who won the National League batting title with a .336 average, had been 11-for-58 (.190) in the postseason.

The Giants' lead didn't last long, as Delmon Young hit a solo homer in the bottom of the sixth to tie the score at 3-3.

Cain lasted seven innings. He allowed three runs and five hits with two walks and five strikeouts.

Scherzer gave up three runs and seven hits in 6 1/3 innings while walking one and striking out eight.

The Tigers were without catcher Alex Avila, who was scratched from the lineup because of a bruised left forearm. He was injured in Game 3 on Saturday night when struck by a foul ball.

Gerald Laird started behind the plate.

The Tigers then lost second baseman Omar Infante in the bottom of the ninth inning when he was in the left hand by a pitch from Santiago Casilla. Infante was diagnosed with a broken hand (fifth metacarpal).

The Tigers were unable to extend the series. They had ace Justin Verlander scheduled to pitch Game 5 in an attempt to push the series back to San Francisco for Games 6 and 7.

"It was big," Posey said of ending the series in four games before Verlander could take the mound again.

NOTES: Giants third baseman Pablo Sandoval was named World Series MVP. He hit three home runs in Game 1, and he batted .500 (8-for-16) in the series. "I was ready for the moment," said Sandoval, who started just one of the five games in the 2010 World Series because he was slumping and had conditioning issues ... Romo saved three of the four World Series games. He wound up with a 0.84 ERA in 10 postseason appearances. ... Theriot was part of a second consecutive World Series championship team. He played for the St. Louis Cardinals in the postseason last year.